1. Field of the Invention
The present invention relates to a control circuit for an opening/closing device in a vehicle and, in particular, to a control circuit for an opening/closing device such as a power window, a sun roof and the like which are equipped in a vehicle.
2. Description of the Related Art
FIG. 1A is a circuit diagram showing a configuration of a conventional control circuit 101 of a power window in a vehicle.
The control circuit 101 is provided with an UP switch 103 which is operated to raise up a glass window of a land vehicle, a DOWN switch 113 which is operated to lower the window glass, a motor 109 which switches over a rotational direction thereof in accordance with a flowing direction of current, a battery power source 107 which stores and supplies an electric energy generated by a power generator equipped in the land vehicle, and an UP relay 105 and a DOWN relay 111 which switches over a contact when a direct current from the battery power source 107 is supplied to an interior coil.
When the UP switch 103 is turned on by a passenger of the land vehicle, a contact of the UP relay 105 is switched over from a state of being in contact with an X side to a state of being in contact with an W side. In this case, the current from the battery power source 107 flows through a terminal W of the UP relay 105, and flows to an I UP direction going from the motor 109, a terminal Z of the DOWN relay 111 to an earth. And then, the motor 109 is rotated in a direction of raising up the glass window in accordance with the flowing direction of current. Thus, during an ON-state of the UP switch 103, the motor 109 continues to rotate so that the glass window is raised up.
On the other hand, when the DOWN switch 113 is turned on by a passenger of the land vehicle, a contact of the DOWN relay 111 is switched over from a state of being in contact with an Z side to a state of being in contact with on an Y side. In this case, the current from the battery power source 107 flows through a terminal Y of the DOWN relay 111, and flows to an I DOWN direction going from the motor 109 and a terminal X of the UP relay 105 to an earth. And then, the motor 109 is rotated in a direction of lowering the glass window in accordance with the flowing direction of current. Thus, during an ON-state of the DOWN switch 113, the motor 109 continues to rotate so that the glass window is lowered.
FIG. 1B is a circuit diagram showing an equivalent circuit in the case where a connecting line between the UP relay 105 and the UP switch 103 short-circuits due to any failures, or in the case where the Up relay 105 is fixed to the terminal W side.
In this case, the connecting line between the UP relay 105 and the UP switch 103 short-circuits; for this reason, this is the same state as the UP switch 103 is turned on. Therefore, the contact of the UP relay 105 is kept at a state of being in contact with the W side. Further, the I UP direction current flows through the motor 109, and then, the motor 109 is rotated to a direction of raising up the glass window.
At this time, when the down switch 113 is turned on by a passenger of the land vehicle, the terminal of the DOWN relay 111 is switched over from a state of being in contact with an Z side to a state of being in contact with on an Y side. However, both terminals of the motor 109 become the same potential; for this reason, no current flows through the motor 109. As a result, even when the DOWN switch 113 is turned, the motor 109 is not rotated; for this reason, the glass window is not lower.
As described above, there has arisen a problem that the glass window is not lowered in the case where a connecting line between the UP relay 105 and the UP switch 103 short-circuits, or in the case where the Up relay 105 is fixed to the terminal W side.
Moreover, a power window system as shown in FIG. 2 has been known as another related art. FIG. 2 is a diagram showing a circuit configuration for open/close driving a window provided in a door on a front passenger seat side.
The power window system is provided with a master control unit 110 which performs control relative to communication and a power window, units 120, 130, 140 and 150, which control a motor for open/close driving a window provided in a door on the driver's seat side in accordance with a switch signal outputted from the master control unit 110. The power window system is constructed in a manner that the master control unit 110 and respective seat units 120, 130, 140 and 150 are mutually connected by means of a multiplex communication line 116, and these units make a communication of a switch state, a switch signal or the like.
First, when a driver assistant seat. DOWN.sub.-- SW (switch) on the driver's seat unit 120 provided the driver's seat side is operated by a driver, the driver's seat unit 120 transmits an ON-switch signal by the DOWN.sub.-- SW to the master control unit 110 via the multiplex communication line 116. Next, the driver's seat unit 120 transmits an OFF-switch signal by a P/WDW lock SW (a power window lock switch) to the master control unit 110 via the multiplex communication line 116.
On the other hand, the master control unit 110 makes a decision that a window operation allowable condition of the front passenger seat is satisfied because the P/WDW lock SW provided on the driver's seat unit 120 is in an OFF-state and an IGN.sub.-- SW (an ignition switch) is in an ON-state, on the basis of the switch signal received via the multiplex communication line 116. And then, the master control unit 110 transmits an open-switch signal for open-driving a P/WDW motor 156 provided on the front passenger seat unit 150 via the multiplex communication line 116.
In the front passenger seat unit 150, a communication IC 151 receives the open-switch signal from the master control unit 110 via the multiplex communication line 111. Based on the received open-switch signal, the communication IC 151 outputs High to a base input of a transistor TR 152 to turn On the transistor 152. As a result, a solenoid coil of a driving relay 153 is excited, and then, a contact "a" of the driving relay 153 is connected to a contact "b" thereof. Further, a power is supplied to a terminal D of the P/WDW motor 156, while the other terminal U thereof is ground because a contact "a" of a driving relay 155 is connected to a contact "c" thereof. As a result, an open-drive current direction from the terminal D to the terminal U flows through the P/WDW motor 156 so that a door window on the driver assistant seat side is open-driven.
Further, when a DOWN.sub.-- SW attached to the communication IC 151 of the front passenger seat unit 150 is turned ON, the communication IC 151 of the front passenger seat unit 150 once transmits an open-switch signal for open-driving the power window on the front passenger seat side to the master control unit 110 via the multiplex communication line 116.
However, according to the aforesaid conventional power window system, in the case where a fault occurs in the multiplex communication line due to any causes and a communication is not made between units, for example, the open-switch signal is not transmitted from the master control unit 110 to the communication IC 151 of the front passenger seat unit 150. As a result, there has arisen that the window is not open-driven by the front passenger seat unit 150.